One of the most widely used way to improve low-temperature properties of diesel fuels is the use of additives. However, a variety of additives and the effect of susceptibility make it difficult to select additive for a particular composition of diesel fuel and operating conditions. The laws of interaction between functional groups of additives and hydrocarbons of the diesel fraction have not been investigated yet. The article discusses the influence of fractional, group and structural-group composition of straight-run diesel fuels on the effectiveness of cold flow improvers. The effect of additives concentration on the effectiveness of their action is considered. It was shown that when selecting a cold flow improver for diesel fuel and determining its optimal concentration, it is necessary to take into account the optimal content of various groups of hydrocarbons in diesel fuel, at which a cold flow improver is most effective.

In this paper, the characteristics of a straight-run diesel fuel sample, narrow diesel fractions, and their blends with a depressant additive are tested and analyzed. The efficiency of the depressant additive action on the low-temperature properties of narrow diesel fractions is evaluated. It is shown that the depressant additive is most effective on the pour point of the heavy diesel fraction (300–360 °C) and cold filter plugging point of the light diesel fraction (180–240 °C). The regularities of the effect of narrow diesel fractions on the effectiveness of the depressant additive are established. It is shown that the addition of narrow diesel fractions has practically no effect on the cloud point of the straight-run diesel fuel sample/depressant additive blend. The addition of narrow diesel fractions has a negative effect on the cold filter plugging point of the straight-run diesel fuel sample/depressant additive blend. The addition of the light diesel fraction and middle diesel fraction (240–300 °C) has no significant effect on the pour point of the straight-run diesel fuel sample/depressant additive blend, but the addition of 5 vol % heavy diesel fraction allows lowering the pour point of the blend by 6 °C. The established regularities are explained from the viewpoint of the depressant additive action mechanism. It was found that for a more effective depressant additive action, it is necessary to take into account the content of various narrow fractions in the composition of diesel fuel. It is established that the simultaneous lightening of the fractional composition of diesel fuel (addition of light fractions and/or removal of heavy fractions) and the addition of a depressant additive to obtain low-freezing diesel fuels is impractical. However, the addition of small amounts of heavy diesel fractions simultaneously with depressant additives increases the possibilities for the production of low-freezing grades of diesel fuel as well as expands the feedstock pool of enterprises for the production of fuel. In the future, the identified regularities of the influence of the narrow diesel fractions will allow us to detail the general mechanism of diesel fuel and depressant additive interaction.

In this paper, the viability of expanding the feedstock base of diesel fuel production by the involvement of the heavy diesel fraction and the use of cold flow improvers was shown. The influence of the heavy diesel fraction content in the diesel fuel composition on its low-temperature properties and the effectiveness of the cold flow improver were studied. It was established that the involvement of a small amount of the heavy diesel fraction (up to 3 vol%) increases the effectiveness of the cold flow improver in relation to the cold filter plugging point. The following recipes of diesel fuel production were recommended: the involvement of up to 5 vol% heavy diesel fraction allows producing fuel of the summer grade; the involvement of up to 5 vol% heavy diesel fraction and the cold flow improver allows producing fuel of the inter-season grade; and the involvement of up to 3 vol% heavy diesel fraction and the cold flow improver to produce fuel of the winter grade.

Zeolites are used as catalysts for a wide range of industrial processes. Due to their microporous structure, the use of zeolites is limited to transformation of light feedstocks. At the same time, light products of oil extraction such as stable gas condensate are burned or returned to the oil reservoir for maintaining reservoir pressure, not being used as a feedstock for the secondary refinery. This work considers the use of the stable gas condensate as a feedstock for the Zeoforming process and the use of the obtained product as one of the blending components of commercial gasoline. After measuring main physicochemical properties and performance characteristics of the stable gas condensate, the Zeoforming process was implemented at a laboratory scale. The use of the stable gas condensate and Zeoforming products as blending components of gasoline was assessed. Applying the software program, recipes for the blending of gasoline were developed. It has been found that the Zeoforming process increases the octane number of the stable gas condensate, allowing for reduction of the gasoline production costs due to replacement of expensive additives.

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